This invention relates to the preparation of semiconductor device structures, particularly to methods of depositing films, such as metal oxide films, using metal or metalloid carboxylate complexes.
Capacitors are the basic energy storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs).
High quality thin oxide films of metals or metalloids, such as barium-strontium-titanates and strontium-bismuth-tantalates, for example, deposited on semiconductor wafers have recently gained interest for use in memories. These materials have very high dielectric constants and excellent resistance to fatigue. They also have suitable properties for a variety of other uses, such as electrooptic materials, pyroelectric materials, and antireflective coatings.
Suitable metal or metalloid oxides are typically delivered to a substrate in the vapor phase; however, many oxides are difficult to deliver using vapor deposition technology. Many precursors are sensitive to thermal decomposition. Also, many precursors have vapor pressures that are too low for effective vapor deposition. Thus, there is a continuing need for methods and materials for the deposition of oxide films using vapor deposition processes on semiconductor structures, particularly random access memory devices.
The present invention is directed to a method of forming a film on a substrate, preferably manufacturing a semiconductor structure, particularly a memory device. The method involves forming a film using a carboxylate complex. Typically and preferably, the film is a dielectric metal- or metalloid-containing material. The metal- or metalloid-containing film can be an oxide, sulfide, selenide, telluride, nitride, or combination thereof Preferably, the film is a metal- or metalloid-containing oxide film. The film can be used as a dielectric layer in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device.
This method involves vaporizing a precursor, preferably a liquid precursor, comprising one or more carboxylate complexes and directing it toward a substrate, such as a semiconductor substrate or substrate assembly, using a chemical vapor deposition technique to form a metal- or metalloid-containing film on a surface of the substrate, wherein the carboxylate complex is of the following formula:
Mn+(OC(O)R1)u(OR2)v{(R3)(R4)N[(CH2)wN(R5)]x(CH2)yN(R6)(R7)}zxe2x80x83xe2x80x83(Formula 1)
or
Mn+(OC(O)R1)u(O)v{(R3)(R4)N[(CH2)wN(R5)]x(CH2)yN(R6)(R7)}zxe2x80x83xe2x80x83(Formula II)
wherein: M is a metal or metalloid; each R is H or an organic group; n+ is the valence oxidation state of the metal or metalloid (typically, 1 to 8); u=1 to n; v=0 to nxe2x88x921; wxe2x88x921 to 5; x=0 to 8; y=1 to 5; z=0 to 5; and u+v =n for Formula I or u+2v=n for Formula II. These carboxylate complexes are neutral complexes and may be liquids or solids. If they are solids, they are preferably sufficiently soluble in an organic solvent to allow for vaporization by flash vaporization, bubbling, microdroplet formation, etc.
This method is particularly well suited for forming films on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. It is to be understood that the method of the present invention is not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, the methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies, can be used in the method of the present invention. These include, for example, fibers, wires, etc. If the substrate is a semiconductor substrate or substrate assembly, the films can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers to the semiconductor substrate having one or more layers or structures formed thereon.
A particularly preferred embodiment of the present invention is a method of depositing a liquid precursor using a chemical vapor deposition involving microdroplet formation. The liquid precursor includes one or more carboxylate complexes of Formulas I or II, which may be liquids or solids dissolved in an organic solvent, for example. The method involves generating microdroplets of the liquid precursor; vaporizing the microdroplets using a heated carrier gas; and directing the vaporized microdroplets toward the substrate to form a film on the substrate.
Also, the present invention provides a chemical vapor deposition precursor comprising two or more carboxylate complexes of Formula I or Formula II above. One particularly preferred chemical vapor deposition precursor comprises: at least one compound of the formula (Formula III) Mn+(OC(O)R1)u(OR2)v wherein M is a metal selected from the group consisting of Group IVB and Group VB, each R is H or an organic group, n=1 to 5, u=1 to n, and v=0 to nxe2x88x921; and at least one compound of the formula (Formula IV) Mn+(OC(O)R1)u{(R3)(R4)N[(CH2)wN(R5)]x(CH2)yN(R6)(R7)}z wherein M is a metal or metalloid selected from the group consisting of Group IA, Group IIA, Group IIIA, Group IIIB, and the lanthanides, each R is H or an organic group, n=1 to 4, u=1 to n,w=1 to 5, x=0 to 8, y=1 to 5, and z=1 to 5.